Various known methods allow a telephone call to be made to a correspondent who wishes to conserve, completely or partially, his/her anonymity. In such a scenario, the telephone number and/or the real identity of the correspondent are not disclosed to the caller who only knows an alias associated with this correspondent.
These methods, such as that described in the international patent application of the applicant published under the number WO 2010/076771, are based on a connection between the two users via a trustworthy third party. This third party, who may for example be the telephone operator, possesses the number of the correspondent and has the role of routing the communication without disclosing to the caller the information relating to the identity of this correspondent.
However, the known methods allowing the anonymity of the correspondent to be preserved are all based on the assumption that the communication is successful in all cases, in other words the correspondent is present and answers the call. It is never envisioned that the correspondent might not be available, may be absent or not accessible.
However, if the correspondent does not answer the call, at the end of a settable time, his/her voicemail is generally activated and a personal welcome message is played which discloses either the identity or the telephone number of the correspondent. There is therefore no conservation of anonymity in such a case. The document US 2008/0025488A1 describes a system for anonymous communications allowing an anonymous communication between a caller and a user being called.
One possible solution to this problem consists in allowing the telephone operator to detect the anonymous nature of the call and to allow a welcome message, different from the standard message, to be played which would disclose neither the identity nor the telephone number of the correspondent. However, such a solution limits the service offered to the subscribers of the telephone operator in question alone, which offers a very limited advantage. Therefore, there exists a need to guarantee the conservation of the anonymity of the correspondent even when his/her voicemail is activated and that is independent of the respective operators of the caller and of the correspondent.